1. Field of the Invention
This invention relates to casting arrangements for splints or supports.
2. General Background and State of the Art
In the field of orthopaedic immobilization assemblies, such as splints and supports, it is well known to use hardenable material, particularly water hardenable material impregnated into high strength fabric, as a splint or support. In practice, a blank or a tape may be impregnated with a water hardenable urethane. At the time when the splint or support is to be applied to the patient, it is dipped into water, applied to the injured part of the anatomy, and, within a few minutes, hardens.
One troublesome problem which has been encountered involves the edges of the impregnated material, which often have frayed fabric or outwardly extending threads or filaments. These frayed edges or outwardly extending threads or filaments become very rigid and sharp as the urethane hardens; and these sharp edges often irritate and scratch the skin of the patient over the extended period of time that the cast or support is in place.
For completeness, reference is made to U.S. Pat. No. 4,800,872, issued Jan. 31, 1989, which discloses the application of very low concentrations of a binder (not more than 90 grams per square meter) to an orthopaedic casting tape. However, spraying broad areas of the tape with the binder would tend to inhibit impregnation of the water hardenable material; and the very low concentrations of the binder do not provide the edges with the desired level of protection for the patient.
It is also recognized that the edges of materials for non-medical applications have been treated heretofore to prevent raveling. However, in the case of orthopaedic casting blanks or tapes, which are impregnated with water hardenable material, once the water hardenable material has been activated, and the blank has been hardened, there is no problem with raveling. Also, it is important for medical orthopaedic uses that the edge treatment material provide a non-rigid edge and be formed of a material which is compatible with contact with the skin and which is sufficiently soft so that it does not scratch or irritate the skin.
Accordingly, a principal object of the invention is to provide a more comfortable cast or support, with edges which do not cut into or irritate the skin of the patient.
In accordance with one illustrative embodiment of the invention, the edges or ends of a casting blank, strip, or tape are treated or impregnated with a non-rigid, material prior to impregnating the casting fabric with the water hardenable material. The casting material can be either a single or multi-layer fabric including fiberglass and/or other high strength fibers. It is also possible to use multiple layers of a single or double layer fabric, or double knit type spacer material. The non-rigid edge material could be a silicone, a rubber, adhesive material, urethane, or other non-rigid or relatively soft material. Once cured, the flexible material binds the filaments of the casting fabric together, thereby creating a sealed edge which is smooth and comfortable. A preferred type of non-rigid material is one in which, after curing, it does not restrict or mask the beneficial properties (i.e., movement, moldability, etc.) of the casting material. Using certain edge treatments, it is possible to block the water hardenable material from the edges of the cast or splint, creating a type of xe2x80x9cflex-edgexe2x80x9d feature which will provide further comfort to the user.
In another illustrative embodiment of the invention, a casting blank may be formed in an irregular configuration for application to a particular portion of the anatomy, and some or all edges thereof may be impregnated with a bead of the non-rigid bonding material. The fabric of the casting blank may be xe2x80x9cspacerxe2x80x9d or double knit type material formed of two spaced layers of knit or woven material with filaments extending between and spacing apart the two layers, and with these filaments being integrally knit or woven into both of the two spaced layers. The casting material may include fiberglass and/or other high strength fibers.
In the formation of the casting blank, and the application of non-rigid bonding material, any of a number of techniques may be used. Thus, the blank may be initially cut to the desired shape, and may thereafter be edge coated with a bead of the preferred non-rigid bonding material. If the bonding material is substantial enough, the edge treatment can extend past the edge of the casting material. One example of this would be a foaming material which would also provide some cushioning. The bonding material may be applied by any number of ways, for example by spraying, brushing, pressing, dipping or the like.
However, because the casting blank is preferably formed of high strength, fairly stiff fibers where the fabric may fray substantially when cut, another method is preferred. This method involves the use of a mold, with two generally flat mating surfaces for receiving a rectangular blank of casting material. One of the two mating surfaces is provided with a groove for receiving the non-rigid cushioning or bonding material, and with the overall configuration of the groove corresponding to the desired outline of the casting blank. The other half of the mold has a mating rib in the same configuration as the groove on the other surface of the mold. In practice, the edge cushioning or treatment material, such as a silicone, rubber, adhesive, urethane, or a non-water hardenable plastic, is applied into the groove, the rectangular casting blank is placed in the mold, and the mold is firmly closed, with the rib forcing the fabric of the casting blank down into the cushioning material so that the rectangular casting blank now has the flexible material impregnated into the fabric in the desired irregular configuration of the final casting blank. After the non-rigid material sets up, either by curing or the evaporation of solvent, the blank is formed by cutting through the sealed area, leaving a non-rigid, non-fraying edge around the periphery of the blank. The irregularly shaped blank is then impregnated with hardenable material. Depending on the bonding material chosen and the method of application, it is possible that only the two surface layers of the edges of the blank will retain any of the bonding material, leaving voids in the inner matrix of the double knit material.
Besides applying the edge treatment to provide comfort around the outer edges of an irregularly shaped blank, the non-rigid bonding material may also be applied to other locations of the casting material, to avoid skin irritation at cutouts through the casting material, and to the longitudinal edges of a strip of casting material, for examples. As an optional advantage, the bonding material may prevent the impregnation of the sealed areas with any water hardenable material giving the eventual support a flexible edge feature. In addition to being useful for sealing the edges of a casting material, the flexible edge material can also be used to secure padding material to one or both sides of the casting material. In practice, before the edge material is applied, the cast material is overlaid with single or multiple layers of a padding type material. The edges are then treated with the non-rigid material which serves to secure all of the layers together.
In the application of the edge treatment to the edges of the casting blank or tape, it is preferably directly applied in a fairly high concentration so that it penetrates and seals the edges but does not extend inwardly over the broad remaining areas of the blank or tape. Preferably the concentration is in the order of at least 400 grams per square meter, up to 10,000 grams per square meter, and preferably between 600 and 3,500 grams per square meter. Normally the edge treatment does not extend inward from the edges for more than one centimeter, or one-quarter inch or one-half inch.
Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description, and from the accompanying drawings.